Multiprocessor communication systems which provide bidirectional communication capabilities for each of the processors using a bidirectional communication link are known. Such systems are often associated with alarm or monitoring functions.
One known form of such a system incorporates a common control unit which is connected to a two-wire electrical cable which extends throughout a region to be monitored. A plurality of detectors can be coupled across the wires of the link at locations corresponding to portions of the region to be monitored. Additionally, output devices can also be coupled across the wires of the link and can be used to provide various output functions such as energizing or de-energizing solenoids or energizing or de-energizing audible or visual annunciators.
It has also been recognized that such communication links at times exhibit deteriorating performance due to shunt impedances or ground faults. While there have been approaches developed in the past which attempt to establish the location of one or more such conditions on Class A loops, it would be desirable to ascertain the existence of shunt impedances across the wires of the link or the location of ground faults in other link configurations. Preferably, it would be desirable to provide such functionality without having to substantially increase the base cost of such systems for a given number of detectors. Additionally, it would be preferred if the desired functionality can be provided without substantially increasing system complexity.